1. Technical Field
The present invention relates in general to automated tooling and, in particular, to communication with automated tools.
2. Description of the Related Art
A DeviceNet™ network is an open, low-level network that provides connections between simple industrial devices, such as sensors and actuators, and higher-level devices, such as Programmable Logic Controllers (PLCs) and computer systems. DeviceNet networks employ a DeviceNet physical layer, a Controller Area Network (CAN) data link layer, DeviceNet transport and network layers, and the Common Industrial Protocol (CIP) at Layer 5 and above. Utilizing this layered network architecture, the DeviceNet network provides control, configuration, and data collection capabilities for industrial devices over a single network. As an open network, DeviceNet also supports the interoperability and common control of diverse intelligent sensors/actuators of multiple vendors over a single network.
A DeviceNet network includes a collection of nodes, each having an associated node number or Media Access Control (MAC) Identifier (ID). The node number of each node is set, for example, using dual in-line package (DIP) switches at each node, and serves as a node priority. Although the DeviceNet standard has been supplemented to support peer-to-peer communication, in many implementations the DeviceNet network has a master/slave configuration in which one or more masters continuously scan a list of slave nodes on the network, issuing Get Attribute service codes (requests) to obtain the current attribute values of the instance(s) of particular objects at the slave nodes. The master(s) implement a control algorithm that, based upon the attribute values obtained from the slave nodes, generates and sets new attribute values for object instances at the slave nodes (via Set Attribute service codes) in order to control future operation of the slave nodes. Further information regarding DeviceNet networks and their operation can be obtained, for example, from Open DeviceNet Vendor Association (ODVA), Inc. of Ann Arbor, Mich.
The DeviceNet standard requires that a certain communication establishment protocol be followed each time a node enters a DeviceNet network. While this requirement enhances communication reliability, the present invention recognizes that the multi-second delay required for the DeviceNet communication establishment protocol is unacceptable, particularly in automated assembly lines or other environments in which nodes are constantly being added to and dropped from the DeviceNet network, for example, as automated tools are connected and disconnected from assembly line robots.